1. Field of the Invention
The invention relates generally to an image forming apparatus configured to check the condition of a developer cartridge installed therein.
2. Description of Related Art
A known developer cartridge may be configured to store toner therein, to be selectively attached to and detached from a known image forming apparatus, such as a laser printer. The known image forming apparatus may be configured to determine a condition of the installed developer cartridge, i.e., whether an installed developer cartridge is a new cartridge or a used cartridge, and to determine a type of the installed developer cartridge.
The known image forming apparatus includes a swingable arm-like actuator, a spring which urges the actuator toward a first position, a sensor configured to detect the swing of the actuator, and a controller configured to determine the condition of the developer cartridge and to determine the type of developer cartridge based on signals outputted from the sensor. The known developer cartridge includes one or two contact protrusions which protrude from a shaft portion, a detection gear configured to rotate about the shaft portion together with the contact protrusion(s), and a gear mechanism configured to engage the detection gear and to transmit a driving force to a developing roller.
For example, when a front cover of the image forming apparatus is closed after the developer cartridge is attached to the main body of the image forming apparatus, the controller performs a warm-up operation including an idle rotation. During the idle rotation, an agitator rotates to agitate toner stored in the developer cartridge.
A transmission force from a drive source, which is provided at the main body of the image forming apparatus, is transmitted to the agitator and to the detection gear, which are provided at the developer cartridge, via the gear mechanism, to perform the idle rotation. By the transmission of the force, the agitator starts the agitation of the toner and the contact protrusion further moves and applies the force to the first end of the actuator, and thus, the contact protrusion disengages from the actuator at a second position. Subsequently, the actuator returns to the first position due to the urging force from the spring. When the developer cartridge includes two contact protrusions, a first of the contact protrusions applies the force to the first end of the actuator, and a second of the contact protrusions then applies a force to the first end of the actuator to further swing the actuator. The second swing of the actuator is detected by the sensor, and a signal detected by the sensor is transmitted to the controller as a second detection signal.
If, however, a user inadvertently rotates the developing roller or a gear positioned in the gear mechanism or the known developer cartridge, the detection gear may rotate in synchronization with the gear mechanism, and the contact protrusion(s) may move to an undesired position(s). Then, the actuator and the sensor may not correctly detect the contact protrusion(s).